A common method of treating temporary or chronic pain is by application of heat to the afflicted area. Such heat treatments are used as a means of therapy for conditions which include aches, stiffness in muscles and joints, nerve pain, rheumatism and the like. These treatments include the use of whirlpools, hot towels, hydrocollators, heating pads and elastic compression bands. Many of these devices employ reusable thermal packs containing, e.g., water and microwaveable gels. In general, such devices which require the thermal source to be replenished are inconvenient to use. Further, many of these thermal units or devices do not provide long lasting heat and also do not maintain a consistent temperature over long periods of time. The skin temperature needs to be maintained from about 38.degree. C. to about 41.degree. C. but not above 45.degree. C., as tissue damage occurs above 45.degree. C., to achieve the desired therapeutic benefits.
The beneficial therapeutic effects from this administration of heat diminishes after the heat source is removed; therefore, it is desirable to provide a sustained heat source to the afflicted area for as long as possible, preferably for about eight hours. Disposable heat packs based on iron oxidation, such as those described in U.S. Pat. Nos. 4,366,804, 4,649,895, 5,046,479, and Re. 32,026 are known and can provide long-lasting heat. However, such devices have proven not totally satisfactory. Many of these devices cannot maintain a consistent and controlled temperature and/or such thermal devices are bulky and have unsatisfactory physical dimensions which hinder their effectiveness. Specifically, such devices cannot be easily incorporated into wraps which can comfortably conform to various body contours and hence deliver inconsistent, inconvenient and/or uncomfortable heat application to the body.
A major reason these heating devices can not maintain a consistent and controlled temperature is due to the considerable empty space within the pack after the pack is filled with the heat generating composition, which inevitably causes uneven distribution or agglomeration of the composition in the pack, especially since these devices generally stand substantially perpendicular or at a slight slant when the heat pack is applied to the body. Uneven distribution of the heat generating composition makes the heat generation in the pack uneven and the agglomeration results in an unpleasant feel to the pack for the user. The agglomeration of the composition also causes uneven heat generation because it disturbs the supply of oxygen to the iron particles which is needed for the oxidation reaction to occur. In order for these heating devices to generate a uniform heat, the heat generating composition must be placed in the pack in a flat form, such as the heat packs of Usui in U.S. Pat. No. 5,046,479. The heat packs of Usui have an air permeability, which allows oxygen to enter the bag while creating a reduction in the pressure within the bag as the oxidation reaction occurs, thereby holding the composition in place and maintaining the bags flat form while applied to the body. This, however, requires very careful selection of both, the components for the particulate composition and the material for the heat pack bag. Specifically, this method allows very little variation in the air permeability of the bag material, which can occur between different manufactured lots of the air permeable material. This method also does nothing to solve the problems associated with controlling the carbon dust or the uniformity of the composition during filling of the heat pack and/or the finished heat pack during use.
In Japanese Kokai Patent Application No. HEI 06-315498, Kodama discloses that, while heat packs having a low packing density have good oxygen permeability and are able to reach their maximum temperature quickly, the temperature decreases rapidly. This is primarily due to the uneven distribution of the heat generating composition within the pack. On the other hand, Kodama discloses that the heat generating composition cannot be packed too densely. If the packing density is high, the heat pack never reaches its highest temperature or maximum duration. This is due to the inability of oxygen to penetrate the heat generating composition beyond its surface, which results in the incomplete reaction of the entire composition, i.e., the center of the composition remains unreacted.
There are several major problems in the manufacture of disposable heat packs, utilizing the exothermic reaction of iron oxidation, wherein the ingredients are blended dry. For example, one major problem is the carbon powder tends to become airborne easily and therefore a problem, in that raw materials are lost and the working environment is hazardous, both for the health and safety of persons working in the manufacturing area of such heat packs. Special facilities must be maintained, as well as, special clothing and equipment must be worn by the manufacturing workers. A second major problem, related to the dry powdered carbon, occurs during the manufacture of the finished heat pack. That is, the powdered carbon tends to fly out of or overflow the intended fill space of the heat pack during the filling process such that the heat pack margins become soiled with carbon dust preventing effective sealing of the powdered exothermic composition inside the finished heat pack. A third problem is maintaining the uniformity of the dry powdered ingredients in the particulate exothermic composition after blending. That is, once uniformly blended, the composition, which contains particles of different weights and densities, may shift or settle during the manufacturing process such that the finished heat pack may not contain a uniform mixture of the composition, thereby reducing the performance of the heat pack. A fourth problem is the lack of fluidity of the dry powder mixture during the manufacturing process, largely due to the electrostatic adherence of the powdered particles to the containers and/or equipment.
One method of reducing these problems is disclosed by Hatsumoto in Japanese Kokai Patent Application No. HEI 06-241575, in which Hatsumoto adds a small percentage of the total water to the carbon before blending it with the other dry ingredients. While this method reduces the amount of carbon dust, it requires that the amount of water added to the carbon, prior to blending, be carefully and precisely measured, and the preferred embodiment requires that the wetted carbon stand for at least 24 hours before blending with the other ingredients. This method, still does not guarantee the uniform content of the particulate exothermic composition or address the other manufacturing problems mentioned above.
Another method of reducing these problems is disclosed by Watabe in Japanese Kokoku Patent No. HEI 05-081261. Watabe utilizes magnetic transfer of pre-wetted powdered ingredients, in the shape and thickness of the desired heat pack, to a sheet of material used for the pack. The remaining water is then sprayed onto the powdered ingredients immediately prior to a second sheet being placed on top of the magnetic sheet containing the wetted ingredients. The sheets are then sealed, enclosing the wetted ingredients to form the desired heat pack. The pack is cut out of the bonded sheets and quickly placed into an oxygen-impermeable protective package. This method is more efficient and less labor intensive than the method of Hatsumoto, but it still can not guarantee the uniform content of the particulate exothermic composition, and requires very specialized machinery.
In another method of reducing these problems Odama discloses, in Japanese Kokai Patent Application No. HEI 04-293989, using a wet granulation method wherein an adhesive binder, such as polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and polyvinylpyrrolidone, is added to water and dissolved, before the water is added to the other ingredients. When the water-binder solution is added to the other ingredients, pellets are formed. These wetted pellets are then packed into gas-permeable bags. This method requires a large amount of water, 55-70parts, by weight of the composition, and binder, 10-20 parts, by weight of the composition, to be added to the exothermic mixture. This reduces the carbon dust and increases the fluidity of the mix, as well as improves the uniformity of the mixture content, but requires careful maintenance of the water added to the composition, as well as an inert atmosphere during the manufacturing process.
The inventor of the present invention has developed dry-compacted heating elements comprising a specific iron oxidation chemistry for incorporation into heat cells having specific physical dimensions and fill characteristics, as well as methods of manufacturing said heating elements and heat cells. These heat cells can be easily incorporated into disposable body wraps and the like, which adapt to a wide variety of body contours, thus providing consistent, convenient, and comfortable heat application. The present invention uses dry agglomeration and/or a direct compaction technique, usually used in the tablet and slugging operations of pharmaceuticals, to overcome the aforementioned problems associated with the current heat packs and their manufacture. Content uniformity of the particulate exothermic composition is maintained through electrostatic and pendular agglomeration, i.e., the enhancement of normal electrostatic forces, by pre-treating the powder blend with low levels of liquefied polysaccharide(s) or modifiers prior to compaction. Once agglomerated, the ingredients are formed as slugs or tablets of a pre-measured, dust-free composition which requires only the on-line addition of water or brine for activation.
Agglomeration of the high surface area powder blend with the low levels of agglomeration aids, such as polysaccharide(s) or modifiers, required in the present invention is unexpected, i.e., the ratio of powder surface area to agglomeration aid is very large and therefore, the use of much higher levels of agglomeration aids should be required. The low levels of agglomeration aids allows for a more efficient use of dry binders, added to the exothermic compositions to aid in the binding together of carbon and iron, and produces a hard compaction without excessive dilution of the reactants.
Alternatively, direct compaction using a roller compactor and chelsenator, a tablet press slugging operation and chelsenator, or roller compactor modified to produce pellets, can be used to produce small granules/pellets, which are useful for a controlled, dust-free packing operation of the heat cells of large size or irregularly shaped configurations. The present invention, which is substantially free of water in the compaction process, reduces the carbon dust, eliminates various manufacturing problems, increases the line speed and fill weight accuracy, improves fluidity of the exothermic composition, eliminates the non-uniformity of the exothermic composition within the finished heat cell, improves the performance of the finished heat cell, and eliminates the need for specialized equipment and environments, all of which significantly reduces the labor required, health and safety hazards, and overall cost of manufacturing.
The heat cells, incorporating heating elements manufactured according to the methods of the present invention and based on a specific iron oxidation chemistry, have specific physical dimensions and fill characteristics, providing long lasting heat generation with improved temperature control. The heat cells contain a dry-compacted particulate heat generating material which substantially fills the available cell volume within the cell reducing any excess void volume thereby minimizing the ability of the heat generating material to shift within the cell. This is accomplished without the need for any differential pressure across the cell wall. These heat cells, because of their adaptable physical dimensions, can be easily incorporated into disposable body wraps and the like which adapt to a wide variety of body contours, thus providing consistent, convenient, and comfortable heat application.
It is therefore an object of the present invention to provide dry, compacted particulate heating elements, and methods of manufacturing said elements, using direct compaction of powdered ingredients, comprising carbonaceous material and iron, capable of reaching their maximum temperature quickly and providing a controlled and sustained temperature, for incorporation into exothermic heat cells. These heat cells are then easily incorporated into disposable body wraps which adapt to a wide variety of body contours providing consistent, convenient and comfortable heat application.
These objectives and additional objectives will become readily apparent from the detailed description which follows.